Abstract

Purpose

Rapid shallow breathing may occur at any time during spontaneous breathing trials (SBT), questioning the utility of a single determination of the rapid shallow breathing index (RSBI). We hypothesize that change in RSBI during SBT may more accurately predict successful extubation than a single determination.

Results

Initial RSBI was similar in Extubation Success and Extubation Failure groups (77.0 ± 4.8, 77.0 ± 4.8, p = ns). Nevertheless, RSBI tended to remain unchanged or decreased in the Extubation Success group; in contrast RSBI tended to increase in the Extubation Failure group because of either increased RR and/or decreased VT (p < 0.001 for mean percent change RSBI over time), indicating worsening of the respiratory pattern. Quantitatively, only 7/63 subjects of the Extubation Success group demonstrated increased RSBI ≥20% at any time during the SBT. In contrast, in the Extubation Failure group, RSBI increased in all subjects during the SBT, and eight of nine subjects demonstrated an increase greater than 20%. Thus, with a 2-h SBT the optimal threshold was a 20% increase (sensitivity = 89%, specificity = 89%). Similar results were obtained at 30 min (threshold = 5% increase). Percent change of RSBI predicted successful extubation even when initial values were ≥105.

Conclusion

Percent change of RSBI during an SBT is a better predictor of successful extubation than a single determination of RSBI.